Athame

Special, sacred knives have a long history of use within magical tradition.  Joseph Peterson, a modern esoteric scholar, attributes the roots of the word “athame” to the Key of Solomon and the use of an “arthame” or consecrated knife can be traced to a 1929 book by Grillot de Givry titled Witchcraft, Magic and Alchemy.  It is possible that Gerald Gardner drew his inspiration for the inclusion of the athame into Wiccan tradition from these or other similar sources.  It is most likely that the use of and inspiration for the word “athame” within modern witchcraft comes from older grimoire traditions such as the previously mentioned Key of Solomon and The Grimoire of Honorius among others.1

The athame is the primary tool of an individual within the Wiccan tradition.  Traditionally it is to be black-handled and double edged, though many within the community have opted for less traditional athames in all kinds of designs.  The athame primarily signifies that any single Witch can cast a circle and work with magic.  It is used to channel energy, extend power and focus will. 
Symbolically the athame is for the individual the equivalent of what a sword would be to a coven.  It is considered a masculine tool due primarily to its phallic nature and is linked with the element of fire.  Most often the athame is made of steel or iron with either a metal or wooden handle, but many varieties that differ from this can be found.2  “In Wicca, both the athame and sword are traditionally double-edged, signifying that a sword ‘cuts both ways’, and keeping us mindful of the dangers and abuses of power, even while we wield it—power must, in the Wiccan view, be accompanied by equal quantities of compassion.”3

The athame is rarely used for actual cutting.  While the athame is used for ritual purpose within a circle it is rarely used to invoke or call upon gods/goddesses, this is because the athame is representative of commanding and power manipulation.4 
There is some controversy over whether the blade should be sharp or if it is acceptable to have a dulled blade.  Some will argue that a dull blade represents a weakening of the will and that the energy raised and directed through the athame will not be as powerful or effective as a true, sharp, double-edged blade.  Others will say that the blade should be dull because an athame is to be used for ritual purpose only, not for cutting or the drawing of blood.  As someone who has used both dull and sharp blades with ritual I can say that personally I have found there to be no difference between the two and have found both to be equally effective, when searching for an athame it is perhaps most important that the blade suits the owner and this requires a certain amount of flexibility and individual consideration.